Hey Chuck.? Have not had a QSO is a long time. Where are you hanging out these days on AM?
W7WRX
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Grid drive one 4-400 with bias and screen voltage.? Then you can run Class C for plate modulation and bias it for AB1 or AB2 operation for SSB amplifier
mode.
?
A Johnson ranger or similar power level ?“boatanchor” would make an ideal driver for the Class C operation.? Lots of schematics available in earlier ARRL
publications for such a set up. I think there was a 4-400A amp in several of the ARRL handbooks from the 1960’s.
?
813’s get squirrely on 15M and above and can be tamed but efficiency drops a bit.
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What are the modulator tubes and which modulation transformer are you going to use?
?
I’ve built several AM rigs in the past ten years and have pictures of them on my QRZ.com page.? Check out the 4-400A rig I designed and built.? Also the
813 rig.
?
-Chuck K1KW
?
From: [email protected] [mailto:[email protected]]
On Behalf Of kc1at via groups.io
Sent: Tuesday, February 04, 2025 6:35 AM
To: [email protected]
Subject: [ham-amplifiers] Dilemma
?
Over the years I've collected parts to build an amplifier. Life got in the way during most those years but now I find myself with the time and ambition to build an amplifier for my boatanchors.
As far as bottles are concerned I have a bunch of 813s a 3-400Z,. couple of 4-400s and of course the usual 811s, 807s, 6146s........Got plenty of iron for a power supply up to 3kv.
Need some direction as to which way to go.? I operate 40 thru 10. Have a soft spot for AM. (yes I'm old) but do CW and SSB.
Finishing up a 350 watt modulator.
OR should I forget all this stuff sell it and buy an amplifier.
|
Grid drive one 4-400 with bias and screen voltage.? Then you can run Class C for plate modulation and bias it for AB1 or AB2 operation for SSB amplifier mode. ? A Johnson ranger or similar power level ?“boatanchor” would make an ideal driver for the Class C operation.? Lots of schematics available in earlier ARRL publications for such a set up. I think there was a 4-400A amp in several of the ARRL handbooks from the 1960’s. ? 813’s get squirrely on 15M and above and can be tamed but efficiency drops a bit. ? What are the modulator tubes and which modulation transformer are you going to use? ? I’ve built several AM rigs in the past ten years and have pictures of them on my QRZ.com page.? Check out the 4-400A rig I designed and built.? Also the 813 rig. ? -Chuck K1KW ?
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From: [email protected] [mailto:[email protected]] On Behalf Of kc1at via groups.io
Sent: Tuesday, February 04, 2025 6:35 AM
To: [email protected]
Subject: [ham-amplifiers] Dilemma ? Over the years I've collected parts to build an amplifier. Life got in the way during most those years but now I find myself with the time and ambition to build an amplifier for my boatanchors. As far as bottles are concerned I have a bunch of 813s a 3-400Z,. couple of 4-400s and of course the usual 811s, 807s, 6146s........Got plenty of iron for a power supply up to 3kv. Need some direction as to which way to go.? I operate 40 thru 10. Have a soft spot for AM. (yes I'm old) but do CW and SSB. Finishing up a 350 watt modulator. OR should I forget all this stuff sell it and buy an amplifier.
|
Are you planning on using the modulator with this amplifier?? ?If so a Single 4-400 will do 550 to 600 carrier and would be a good match for that 350-watt modulator for AM. It's a simple circuit.? With added Bias, you can run it in AB and use it on SSB.
C
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I would sell all your tubes and buy 1? ?8877.? Just my opinion.
Over the years I've collected parts to build an amplifier. Life got in the way during most those years but now I find myself with the time and ambition to build an amplifier for my boatanchors.
?
As far as bottles are concerned I have a bunch of 813s a 3-400Z,. couple of 4-400s and of course the usual 811s, 807s, 6146s........Got plenty of iron for a power supply up to 3kv.
?
Need some direction as to which way to go.? I operate 40 thru 10. Have a soft spot for AM. (yes I'm old) but do CW and SSB.
?
Finishing up a 350 watt modulator.
?
OR should I forget all this stuff sell it and buy an amplifier.
?
don
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I would sell all your tubes and buy 1? ?8877.? Just my opinion.
Over the years I've collected parts to build an amplifier. Life got in the way during most those years but now I find myself with the time and ambition to build an amplifier for my boatanchors.
?
As far as bottles are concerned I have a bunch of 813s a 3-400Z,. couple of 4-400s and of course the usual 811s, 807s, 6146s........Got plenty of iron for a power supply up to 3kv.
?
Need some direction as to which way to go.? I operate 40 thru 10. Have a soft spot for AM. (yes I'm old) but do CW and SSB.
?
Finishing up a 350 watt modulator.
?
OR should I forget all this stuff sell it and buy an amplifier.
?
don
|
Don, ????????? You have some mighty fine tubes to make up a bunch of nice amplifiers. My old mentor, Eric, WA4VVI(SK) would run 4 813’s at 4KV! I have an RCA SB-1K Radiomarine amp that uses 3-400Zs and lazily will do a 1KW at 2800VDC. 4-400s you could tie the grids together and with a little extra drive, make a fine amp. So your possibilities are endless. Yes, I run AM also, (my primary mode!). ? Mod-U-Lator, Mike(y)/W3SLK ? ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of kc1at via groups.io
Sent: Tuesday, February 4, 2025 6:35 AM
To: [email protected]
Subject: [ham-amplifiers] Dilemma ? Over the years I've collected parts to build an amplifier. Life got in the way during most those years but now I find myself with the time and ambition to build an amplifier for my boatanchors. As far as bottles are concerned I have a bunch of 813s a 3-400Z,. couple of 4-400s and of course the usual 811s, 807s, 6146s........Got plenty of iron for a power supply up to 3kv. Need some direction as to which way to go.? I operate 40 thru 10. Have a soft spot for AM. (yes I'm old) but do CW and SSB. Finishing up a 350 watt modulator. OR should I forget all this stuff sell it and buy an amplifier.
|
Over the years I've collected parts to build an amplifier. Life got in the way during most those years but now I find myself with the time and ambition to build an amplifier for my boatanchors.
?
As far as bottles are concerned I have a bunch of 813s a 3-400Z,. couple of 4-400s and of course the usual 811s, 807s, 6146s........Got plenty of iron for a power supply up to 3kv.
?
Need some direction as to which way to go.? I operate 40 thru 10. Have a soft spot for AM. (yes I'm old) but do CW and SSB.
?
Finishing up a 350 watt modulator.
?
OR should I forget all this stuff sell it and buy an amplifier.
?
don
|
Sideband Engineers SB-2LA
This one is from 1965:
A ham I know says his ant relay is stuck, its an open frame relay
he says. Probably no parts for this one around anymore?
--
Steve Hearns [ KA2PTE ]
Technotronic Dimensions, VT [USA]
WWW.TECHNOTRONIC-DIMENSIONS.COM
E-Mail: Steve@...
|
Update: ?Southeastern VHF Society 2025 Conference Announcement & Call For Papers
#2MAmplifier
The timeline for submission of papers and presentations has been extended to March 17th.
|
Re: Smoker contamination removal
Removed the tube sub-chassis, and have it soaking in the Fan-monia bucket....
its really got a lot of buildup as the blower was throwing it all right in there.
I got a new blower from ACOM recently, and I soaked down the rest of the chassis
frame, and cleaned it with the Fan-Monia....hard to tell there was any contamination
at all in there now.
--
Steve Hearns [ KA2PTE ]
Technotronic Dimensions, VT [USA]
Authorized ACOM Service center
WWW.TECHNOTRONIC-DIMENSIONS.COM
E-Mail: Steve@...
|
The 3-500zg tube with the graphite plate can handle 600ma ICAS ? The regular 3-500 rated 450ma CCS! ?With enough cooling (very important factor) you could run 2000 watts pep output SSB with a pair of tubes. ?Most vintage amps do not have the transformer capability of this anyhow except for the older Henry amps that can do this. ?
On Friday, January 31, 2025, 12:50 AM, Fran?ois via groups.io <18471@...> wrote: > Attached, please find a great book about tubed amplifiers. ? Hello ? Thank you for this communication. ? Even if it does not answer my question, this document is very interesting, both at the technological and implementation level. ? I reformulate my initial questions: ·???????? What is the maximum anode current (reasonable) for a 3-500Z tube ·???????? What maximum current can be used in a Drake L 7 to bake the tubes (not in RF operation), compared to the transformer capacity for example. ? I measured some characteristics of the HV transformer (measured in short circuit) ·???????? Transformation ratio o?? In CW: 2.95 o?? In SSB: 4.14 ·???????? Resistance brought back to the secondary o?? In CW: 13.4 ? o?? In SSB: 18.6 ? ? ? De la part de HaL Mandel via groups.io
贰苍惫辞测é?: jeudi 30 janvier 2025 21:30
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The original? C41 cap (47 pf) is failure prone.? ?Replace it with a 50 pf TX doorknob cap.? ?The original cap? was made from pc board.
C42? ( 307 pf)? is used to pad the TUNE cap on 160m only.? ?It's failure prone too.? ?Replace it with a 300 pf doorknob.
C39 and C40? will eventually fail.? ?Replace? with a pair of 1000 pf @ 5/7.5 kv doorknobs.? ?The original caps were discs types.?
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Re: Commander HF-2500 Plate Choke
The 3 x section choke,? currently sold by ameritron,? is now screwed up.? Ameritron ran outa 28 ga wire...and started using 27 ga wire.? ?The pair of gaps is way less.? Steve at RF parts got a ton of the screwed up ones....and sent me one to test on my vna.? ?The screwed up version series resonates on 20m and 17m.? Scott got one of the screwed up versions and tossed it.?
The ONLY version of that choke that is wound correctly is sold by W8JI? at CTR engineering.?
I got 2 from RF parts years ago....and tested both of em on the VNA.? ?They resonate at aprx 12.5 mhz...and also 16.5 mhz.? Normal.
Interestingly enough, the 154 uh plate choke in all 4 of my L4B's? ?resonates at 12.5 mhz...and 16.5 mhz.? ? The drake choke is just one winding.?
Now how a good ameritron choke resonates on 30m band, on older alpha's is beyond me.? Close proximity to metal, and / or dielectrics will? shift the resonant freqs down.
The ameritron choke is 6" tall....and is too tall for the L4B.? Barely any clearance between top screw on choke...and top lid.?
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> Attached, please find a great book about tubed amplifiers. ? Hello ? Thank you for this communication. ? Even if it does not answer my question, this document is very interesting, both at the technological and implementation level. ? I reformulate my initial questions: ·???????? What is the maximum anode current (reasonable) for a 3-500Z tube ·???????? What maximum current can be used in a Drake L 7 to bake the tubes (not in RF operation), compared to the transformer capacity for example. ? I measured some characteristics of the HV transformer (measured in short circuit) ·???????? Transformation ratio o?? In CW: 2.95 o?? In SSB: 4.14 ·???????? Resistance brought back to the secondary o?? In CW: 13.4 ? o?? In SSB: 18.6 ? ? ? De la part de HaL Mandel via groups.io
贰苍惫辞测é?: jeudi 30 janvier 2025 21:30
|
Re: Commander HF-2500 Plate Choke
Dear? Riki,
?
Tom, W8JI,
W8JI
W8JI
https://www.w8ji.com
?
is a coil-winder from Days Gone By.
?
Look up his website and see the variety of
RF Chokes he offers.
?
Hal Mandel
W4HBM
|
Dear Francois,
?
Attached, please find a great book about tubed amplifiers.
?
’73,
?
Hal Mandel
W4HBM
|
I am still studying a way to cook my 3-500Z which have not been hot for at least 15 years. The idea is to cook at high current with a low anode voltage, without HF. ? The maximum rating of the cathode current is not clear in the Eimac specifications. There are examples with a current of 0.4 A (for one tube). ·???????? Does this current (0.4 A) seem acceptable to you? ·???????? Can we go beyond that? This requires a grid voltage of around +30/+40V 100 mA. So 4 W and the tube is given for 20W ? I am considering using, temporarily, another transformer, with a lower secondary voltage, upstream of the doubler. ? Is this a bad idea?
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Yes, a “single diode path” would have made it clearer. Thanks for the clarification. What I understood is that these diodes are used to protect the galvanometers in the event of an arc in the PA De la part de Peter Voelpel
贰苍惫辞测é?: jeudi 30 janvier 2025 00:42
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Re: Commander HF-2500 Plate Choke
Hi Riki
I own a 1990 HF-2500 which I got from the estate of a local ham
many years ago. I had a question about it on this forum last week
but through perseverance and much hair pulling, I managed to
resolve it.
Anyway, when I got the amp, there was a spare plate choke with
it. It is different to the one in the amp. It is on a 4" long, 1"
diameter former and it is a single layer coil with a tap point
about 30% up from the bottom and there was a orange 100pF/10kV Z5U
ceramic capacitor which came with the choke. I assume that his
capacitor is connected to that tap on the coil.
I don't need the choke. The one in my amp is fine and if it ever
does go bad, then I would replace it with one of W8JI's chokes,
which I'm sure work work in that location, especially since the
amp does not have 12, 17 and 30m.
I am happy to post it to you for the cost of the postage from
Australia. It would take around 2 weeks to get to you via ordinaly
parcel post. I could also send it express if you wanted it
quicker.
Email me direct at vk6apk@... if you think it would be
suitable. I'm happy to take pics and email them to you direct.
73, Alek VK6APK.
On 30/01/2025 1:26 pm, Riki, K7NJ via
groups.io wrote:
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Somebody who previously owned my Commander HF-2500 replaced
the carbon resistors in the plate parasitic chokes with a
different type of resistor.? This worked fine on low frequencies
160M, 80M, and 40M.? ?When I used the amplifier on 10M, it
became very unstable, most likely with a parasitic oscillation
and caused the plate blocking capacitor to explode and catch on
fire. The main fuses blew, as well as the one on the board that
contains the bias and control circuitry.? After replacing these
fuses and installing carbon resistors in the parasitic
suppressors, I found that the amplifier would no longer work on
80M.? Eventually, I discovered some discolored places on the
plate RF choke where it had evidently arced through its
insulation causing the needed 10M high impedance to shift.? The
choke was replaced? with one I had from another Commander
HF-2500 that has been a source of spare parts.? While trying to
do this, the windings (there's more than one - rather complex
winding - some over the top of others) became loose, and I
unsuccessfully spent several hours trying to get the windings
back like they were and tight on the form they were wound on.?
Even though not satisfied with the replacement choke with loose
and sloppy windings, I tried the amplifier on all the usual
bands starting at 160M and up to 10M.? It seems to work fine up
through 15M, but the 10M band doesn't tune properly - most
likely because the plate choke was still a problem.
?
Does anybody have an original Commander HF-2500 plate choke
that they would like to sell or know where I might find one??
Another possibility is to substitute a different plate choke
that works well in another amplifier with similar plate
parameters. Probably the big challenge in using a different
choke would be to mechanically fit it into the rather crowded
place in the Commander. Another possibility would be to add a
second plate RF choke with a high impedance on 10M in series
with the other choke, but this still might be problematical due
to the tendency of the big choke to break down as before.
Suggestions, especially from anyone who has successfully used a
different choke in the Commander, would be very much
appreciated.
73, Riki K7NJ
?
?
?
|
Commander HF-2500 Plate Choke
Somebody who previously owned my Commander HF-2500 replaced the carbon resistors in the plate parasitic chokes with a different type of resistor.? This worked fine on low frequencies 160M, 80M, and 40M.? ?When I used the amplifier on 10M, it became very unstable, most likely with a parasitic oscillation and caused the plate blocking capacitor to explode and catch on fire. The main fuses blew, as well as the one on the board that contains the bias and control circuitry.? After replacing these fuses and installing carbon resistors in the parasitic suppressors, I found that the amplifier would no longer work on 80M.? Eventually, I discovered some discolored places on the plate RF choke where it had evidently arced through its insulation causing the needed 10M high impedance to shift.? The choke was replaced? with one I had from another Commander HF-2500 that has been a source of spare parts.? While trying to do this, the windings (there's more than one - rather complex winding - some over the top of others) became loose, and I unsuccessfully spent several hours trying to get the windings back like they were and tight on the form they were wound on.? Even though not satisfied with the replacement choke with loose and sloppy windings, I tried the amplifier on all the usual bands starting at 160M and up to 10M.? It seems to work fine up through 15M, but the 10M band doesn't tune properly - most likely because the plate choke was still a problem.
?
Does anybody have an original Commander HF-2500 plate choke that they would like to sell or know where I might find one?? Another possibility is to substitute a different plate choke that works well in another amplifier with similar plate parameters. Probably the big challenge in using a different choke would be to mechanically fit it into the rather crowded place in the Commander. Another possibility would be to add a second plate RF choke with a high impedance on 10M in series with the other choke, but this still might be problematical due to the tendency of the big choke to break down as before. Suggestions, especially from anyone who has successfully used a different choke in the Commander, would be very much appreciated.
73, Riki K7NJ
?
?
?
|
Yes, a “single diode path” would have made it clearer.
Here more then 0.7V are clamped, depends on the meter or meter shunt for grid current.
Zener diode can be used as well or a germanium diode for less then 0.7V.
I was also referring to the “green” diode of your drawing.
?
73
Peter, DJ7WW
?
?
?
?
?
-----Original-Nachricht-----
Betreff: Re: [ham-amplifiers] Drake L-7
Datum: 2025-01-29T20:36:58+0100
Von: "Fran?ois via groups.io" <18471@...>
An: "[email protected]" <[email protected]>
?
?
?
>That clamp diode is typically a single diode.
http://radiojim.exofire.net/pages/Glitch%20diodes.html
De la part de Peter Voelpel
贰苍惫辞测é?: mercredi 29 janvier 2025 18:37
? ?
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Technotronic Dimensions
Robin Midgett
HaL Mandel